1. Field of the Invention
The present invention concerns a composition of additives in small concentration in an ink used for inkjet printing. In one aspect the composition of a UV-absorber, a free radical inhibitor and an antioxidant are added to a liquid ink composition. Upon spaying the ink into the paper, the ink shows improved colorfastness and durability. In another aspect the composition is coated on the printing medium (e.g. paper, plastic) to react with ink when the ink from the printer contacts the medium. The sprayed ink shows improved colorfastness and durability.
2. Description of Related Art
Ink additive--The use of inkjet printing systems has grown dramatically in recent years. This growth is attributed to substantial improvements in print resolution and overall print quality, coupled with appreciable reduction in cost. Today's inkjet printers offer acceptable print quality for many industrial, commercial, business, and residential applications at competitive time and cost. Intensive research and development efforts continue toward improving light fastness of inkjet images. In general light fastness of inkjet images still falls short of that produced by other technologies such as electrophotography or gravure printing. A continued demand in inkjet printing has resulted in the need to develop reliable printers capable of producing high quality colorfast (lightfast) and durable images at a reasonable cost.
An inkjet image is formed when a precise pattern of dots is ejected from a drop generating device known as a "print-head" onto a printing medium. The typical inkjet printhead has an array of precisely formed nozzles located on a nozzle plate and attached to an inkjet printhead substrate. The substrate incorporates an array of firing chambers that receive liquid ink (colorants, pigments and/or dyes dissolved or dispersed in a solvent) through fluid communication with one or more ink reservoirs. Each chamber has a thin-film resistor, known as a "firing resistor" located opposite the nozzle so ink can collect between the firing resistor and the nozzle. In particular, each resistor element, which is typically a pad of a resistive material measures about 35 .mu.m.times.35 .mu.m. The printhead is held and protected by an outer packaging referred to as a print cartridge, i.e., inkjet pen.
Upon energizing of a particular resistor element a droplet of ink is expelled through the nozzle toward the print medium, e.g., paper, transparent film, or the like. The firing of ink droplets is typically under the control of a microprocessor, the signals of which are conveyed by electrical traces to the resistor elements, thereby forming alphanumeric and other characters on the print medium.
The fine tolerances of the nozzles, typically 30 to 40 .mu.m diameter, require that the ink not clog the nozzles. Further, repeated firings of the resistor elements must withstand millions of firings over the life of the ink cartridge to be commercially practical. This also can result in fouling of the resistor elements and degrading pen performance. The build up of residue on the resistor elements is unique to inkjet printers and is known as "kogation" and defined as the build up of residue (kogo) on the resistor surface. The ink composition must be capable of interacting with the print medium, especially paper to penetrate the paper without undue spreading and a subsequent decrease in print quality. Furthermore, in order to maintain the integrity of the printed image over time, it is important that the colorant is lightfast. Inks are known which posses one or more of the foregoing properties.
However, few ink compositions are known that possess all the foregoing desired properties. This is because an improvement in one property often results in the degradation of another property. For example, U.S. Pat. Nos. 4,694,302 and 5,062,892 disclose dyes such as Food Black 2 and ICI (now Zeneca) 286/287 for use in black inkjet inks. Although these inks have been useful in the past, they either suffer from extremely poor color (or light) fastness or slight light fastness improvements at the expense of inkjet pen (print cartridge) performance.
Thus, many inks now commercially used represent a compromise in an attempt to achieve an ink evidencing at least an adequate response in each of the performance attributes such as light fastness and pen performance. None of these ink offer both outstanding light fastness and acceptable pen performance.
Accordingly, research continues into developing ink formulations which have improved properties and which do not improve one property at the expense of the others. Thus, the challenge remains to further improve the colorfastness (or lightfastness) of the inkjet print without sacrificing pen performance and reliability.
Additional Coating on Substrate--The demand for color ink and black ink printers is increasing. The inkjet printer having a non-impact recording system is preferred. This is because of its capabilities in rapid color recording for its system. However, there are still many problems for obtaining and maintaining acceptable multicolor images in high speed recording.
From the standpoint of using a speciality substrate e.g., or paper or plastic, these papers must have colorfastness, sufficient ink-absorbency and dryability. In order to solve the problems of superposing the plural ink droplets and of increasing the number of ink droplets per unit area, it is required that the ink-absorptive capacity is excellent. Owing to the high speed recording rapid drying of the ink after the fixing is necessary. Meanwhile, inkjet recording papers are mainly divided into two groups. One is the plain type ink jet recording paper, which consists of cellulosic fibers or of cellulosic fibers and a filler in order that inks may be absorbed in the space between fibers or spaces which are formed fiber and filler. The other paper is the coated type inkjet recording paper, which consists of paper, a substrate and coating materials, which consists of pigment and binder, in order that inks may be absorbed in a fine void of the coating layer. Although the coated type recording paper provides a small spread and a circular form of ink dot, as well as a high resolution ink absorption rate. Hence the paper has the drawback that it is unsuitable for the multi-color printing using a large amount of ink and is too expensive.
Recently, the demand of plain type papers excellent in the economics, paper-like figures and feeling has increased with high speed printing.
Some art of interest are these areas include:
C. A. MacLeod in U.S. Pat. No. 5,725,641 discloses speciality lightfast inks for inkjet printing.
M. Sakaki et al. in U.S. Pat. No. 5,266,383 disclose a recording medium inkjet recording method.
Y. Kojima et al. in U.S. Pat. No. 5,180,624 disclose a multilayer inkjet recording paper.
M. Sakaki et al. in U.S. Pat. No. 5,266,383 disclose a recording medium inkjet recording method.
K. Yasuda et al. in U.S. Pat. No. 5,213,873 disclose an aqueous inkjet recording sheet capable of recording clear brilliant color images having high durability and resistance to curling and undulations.
F. M. Winnik, U.S. Pat. No. 5,275,647 discloses inkjet compositions containing dye-colored micelles.
B. L. Bradley et al., U.S. Pat. No. 5,254,160 discloses magenta dye inkjet and color set.
H. Morimoto et al., Japanese Kokoi Patent JP 09217033 A2, (Aug. 19, 1997).
C. M. Hesler et al., UK Patent Application GB 2305929 A1, (Apr. 12, 1997).
A. Onodera, et al., Japanese Kokoi Patent JP 09059552 A2, (Mar. 4, 1997).
T. Ooi et al., Japanese Kokoi Patent JP 07164729 A2, (Jun. 27, 1995).
A. Onodera, et al., Japanese Kokoi Patent JP 10036728 A2, (Feb. 10, 1998).
S. Hazana et al., Japanese Kokoi Patent JP 10017802 A2, (Jan. 20, 1998).
D. Ishibashi et al., Japanese Kokoi Patent JP 09324146 A2, (Dec. 16, 1997).
S. Nishihara et al., Japanese Kokoi Patent JP 09272832 A2, (Oct. 21, 1997).
A. Onodera et al., Japanese Kokoi Patent JP 09241558 A2, (Sep. 16, 1977).
H. Ninomya et al., Japanese Kokoi Patent JP 09241553 A2, (Sep. 16, 1997).
T. Shimomura et al., Japanese Kokoi Patent JP 07133452 A2, (May 23, 1995).
S. Koike et al., European Patent Application 583133 A1, (Feb. 16, 1994).
K. Sherota, et al., Japanese Kokoi Patent JP 05345872 A2, (Feb. 27, 1993).
P. Gregory et al., European Patent EP 559310 A1, (Sep. 8, 1993).
J. Murata et al., Japanese Kokoi Patent JP 05169854 A2, (Jul. 9, 1993).
T. Abe et al., European Patent EP 544301 Al, (Jun. 2, 1993).
T. Eida et al., European Patent EP 490195, (Jun. 17, 1992).
N. Nakayama et al., Japanese Kokoi Patent 04091988 A2, (Mar. 25, 1992).
H. Nakano, Japanese Kokoi Patents JP 04065279 A2, (Mar. 2, 1992), JP 04065278 A2, (Mar. 2, 1992), and JP 04065277 A2, (Mar. 2, 1992).
H. Kawashita et al., Japanese Kokoi Patent JP 03122171 A2, (May 24, 1991).
Y. Tomii et al., Japanese Kokoi Patent JP 03192156 A2, (Aug. 22, 1991).
None of these references, individually or collectively, teach or suggest the present invention.
All articles, patents, patent applications, references, standards, and the like cited herein are hereby incorporated by reference in their entirely.
It is apparent from the above description that an ink composition having improved colorfastness and durability is still needed. The present invention provides a composition to achieve such improved printed image qualities.